The present invention relates to a lubricating oil cooling system for a liquid cooled internal combustion engine incorporated in an automotive vehicle such as a passenger car, and more particularly relates to such a lubricating oil cooling system which is suitable for utilization in an automotive vehicle which has its liquid cooled internal combustion engine located behind at least part of the passenger compartment of said vehicle, as, for example, a rear engined or mid engined passenger automobile.
Rear engined and mid engined automobiles are becoming relatively popular in recent times. In these rear and mid engined automobiles, certain problems arise with respect to provision of adequate cooling for the lubricant oil in the engine, because the considerable draft of air caused by the relative wind due to the forward motion of the vehicle does not give such a high cooling effect to the engine, particularly to the lower parts of the engine where the lubricating oil pan is located as in the front engined automobiles. Accordingly there is a risk that the temperature of the lubricating oil should rise so high as to reach an undesirably high value which can cause loss of lubricating quality of the lubricating oil and breakdown of the proper film of lubricating oil required to keep the relatively moving parts of the engine separated and functioning smoothly without undue friction.
As a device for restricting the rise in temperature of the lubricating oil of the internal combustion engine in a rear engined or mid engined automotive vehicle, a per se well known lubricating oil cooling device commonly called a heat exchanger or oil cooler might be considered for application. Now, in the case of a rear engined or mid engined automotive vehicle, the application of an air cooled heat exchanger is not suitable, because as explained above no strong air current will be available unless such an air cooled heat exchanger is provided at the front end portion of the vehicle, but it is undesirable for the lubricating oil passages to be so very long as would be required if such an air cooled heat exchanger were mounted at the front end of the vehicle to receive the impact of a strong draft thereupon. Thus, in the case of such a vehicle, it is desirable to use a a cooling fluid cooled type of heat exchanger for the lubricating oil, provided that the engine is of a cooling fluid cooled type.
However, in the design of the circulation system for the cooling fluid of such a rear engined or mid engined automotive vehicle, problems also arise with regard to minimizing the flow resistance thereof, since inevitably the cooling fluid passage system leading heated cooling fluid from the internal combustion engine to the radiator, and leading cooled cooling fluid back from the radiator to the internal combustion engine, is required to be considerably long, since the radiator is required to be at the front end of the vehicle so as to receive a good draft of air. These problems can be overcome; but the incorporation of a conventional type of cooling fluid cooled heat exchanger for the lubricating oil in such a construction gives rise to additional problems with regard to increasing the flow resistance of the cooling fluid passage system. Accordingly, the integration of such a lubricating oil heat exchanger into the cooling system of a rear engined or mid engined vehicle requires an inventive development.